1. Field of the Invention
This invention is in the field of metering devices and metering methods for controlling the flow of molten metal from a reservoir to a casting mold, and utilizing computer generated signals dependent upon the pressure conditions existing in the reservoir.
2. Description of the Prior Art
Pressure control means for casting devices, particularly for low pressure casting of aluminum have been developed but, for the most part, these have the disadvantage that they do not respond promptly and accurately to the variables such as the amount of metal in the reservoir, pressure and the speed of filling of the casting mold. Consequently, the casting may be non-uniform because the casting variables are not accurately reproduced so the castings may vary from each other as to shape and quality.
There is a regulating device known in which during the interval between two casting operations, a correction of the gas pressure in the reservoir is undertaken because of the decreased level of the molten bath in the reservoir. An exact regulation of greater volumes within small units of time is, however, not possible when using electrically regulated valves.
Such prior art devices frequently make use of two pressurizing steps, a higher pressure to bring the melt out of the reservoir into the casting mold, and a lower pressure in order to fill the mold (see, for example, German Laid Open Specificaton No. 2,435,734). In this type of system, prior art valves may be utilized as discussed in German Laid Open Specificaton No. 1,558,166 which cooperate with two control valves for the two different pressure steps.